I very much love this shop and hope it doesn't close as has been rumored. I partially got into autographs from visiting it, though that was a long time ago.
I think that some here haven't realized some of the benefits the store has in the theming of Hollywood Studios. Lots of places in Hollywood have dozens upon dozens of celeb autographs lining the walls, and that is a great way for Disney to represent some stars that aren't represented elsewhere, whether they were Disney stars or not. You can learn a lot about movie stars from this place from modern to classic, and anything that does that I see as a major positive.
Also, though I know Disney is always interested in the bottom line, and making money Sids does serve a purpose. As many said many of the stores sell the same merchandise, but Sids has unique memorabilia not found anywhere else in the park. They even allow you to photograph the autographs which the place at Downtown Disney never allowed. Time is money at WDW, and if one store draws curious people in to look at and learn about stars, then that makes Toy Story Mania or Tower of Terror or RocknRoller Coasters lines shorter. The point to theme parks is to occupy peoples times with things that are fun, so they aren't bored.
The autographs in the store are over priced from what I know, though in odd ways. It's more based on star power and not based on autograph value. Marilyn's autograph is quite expensive, and is expensive at Sids. Garbo however is astronomically more rare, and Garbo was a huge star, but her auitograph was once being sold for less then Marilyn's in Sids. Because Garbo was so reclusive, her autograph is usually a lot more then Marilyn's at auction houses and such. Also many warn that 90% of all autographs sold on Ebay are fakes. Not being able to see an autograph you are buying can be very, very risky.
The way I looked at it, Disney put a price tag on the autograph, not so much because they thought iot was worth that, but because that's the trouble they'd have to go to to go hunt down another. If the autograph didn't sell, it still was a draw. If it did, then they have some money to go out and find another one they are confident is real then. Even if it didn't sell the autographs and just displayed them, that would be interesting, and then it could sell more mainstream items inside it like John Wayne/Marilyn Monroe/ Wizard of Oz merchandise.
I love Disney, and it should first and for most be present in the parks. But, Walt is not the only thing that made Hollywood, Hollywood. He'd even admit to that. It's important those items/movies/people are represented as well.
Hopefully they keep it, as it does represent something commonly found in Hollywood, and also allows for some stars not in the rest of the park to get some TLC.